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A216529
Numbers n such that (10^n-1)/9 is prime and can be written in the form a^2 + 3*b^2.
0
19, 49081, 109297, 270343
OFFSET
1,1
COMMENTS
The exponent is congruent to 1 mod 3.
PROG
(PARI) is(n)=my(t=10^n\9); ispseudoprime(t) && #bnfisintnorm(bnfinit(z^2+z+1), t) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Sequence in context: A172762 A203703 A068734 * A145851 A182374 A034207
KEYWORD
nonn
AUTHOR
V. Raman, Sep 08 2012
STATUS
approved